Vulnerability · Published Feb 3, 2026 · Assigned by GitHub_M

CVE-2026-25224Fastify Vulnerable to DoS via Unbounded Memory Allocation in sendWebStream

Low 3.7

In plain English

A low-severity resource allocation without limits in fastify from fastify. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 46% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)3.7Low

Exploit odds (30 days)0.5%top 54.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.3, a denial-of-service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a ReadableStream (or Response with a Web Stream body) via reply.send() are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation. This issue has been patched in version 5.7.3.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	fastify	5.7.3	GHSA-mrq3-vjjr-p77c

Affected products (as reported)

Vendor	Product	Versions
fastify	fastify	< 5.7.3

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

References

https://github.com/fastify/fastify/security/advisories/GHSA-mrq3-vjjr-p77c x_refsource_CONFIRM
https://github.com/fastify/fastify/commit/eb11156396f6a5fedaceed0140aed2b7f026be37 x_refsource_MISC
https://hackerone.com/reports/3524779 x_refsource_MISC